Virus infections may give rise to a great number of diseases that produces serious danger for health and existence of mankind. For the last 20 years no less than 30 brand-new infectious agents have been registered, such as: HIV, viral hepatitis, acute and chronic diarrhea, hemorrhagic fever (Ebola, Venezuelan, Brazilian, Rift valleys) [a) Lednicky J. A., Rayner J. O. Uncommon respiratory pathogens. Curr. Opin. Pulm. Med. 2006, 12(3), 235-239. b) Hayden F. G. Respiratory viral threats. Curr. Opin. Infect. Dis. 2006, 19(2), 169-178]. In particular, special anxiety is caused by the risk of infection by so named avian influenza. [a) Liu J. P. Avian influenza-a pandemic waiting to happen? J. Microbiol. Immunol. Infect. 2006, 39(1), 4-10. b) Henter J. I.; Chow C. B.; Leung C. W, Lau Y. L. Cytotoxic therapy for severe avian influenza A (H5N1) infection. Lancet. 2006 367(9513), 870-873. Review]. According to statistical data, 60-65% of epidemic infections have viral ethiology. Because of the complexity of interactions in triad “virus—host's organism—drug”, most of modern antiviral drugs demonstrate side effects in the course of therapy and promote resistant virus strains [Jain R., Clark N. M., Diaz-Linares M., Grim S. A. Limitations of current antiretroviral agents and opportunities for development. Curr. Pharm. Des. 2006, 12(9), 1065-1074.]. At present, the number of antiviral drugs that could be used in clinical practice is extremely limited—only 43 low molecular weight substances [http://integrity.prous.com/integrity], that is far from satisfying requirements of prophylaxis and treatment of virus diseases. Moreover, there are considerable number of virus infections initiating all kind of diseases for treatment of which chemotherapeutic agents are absent. It is referred, for example, to the diseases caused by viruses of papilloma, adenoviruses, herpes-6, variola, syndrome SARS, hemorrhagic fevers, fever of the Western Nile, avian influenza [De Clercq E. Recent highlights in the development of new antiviral drugs. Curr Opin Microbiol. 2005, 8(5), 552-560].
Thus, the development of new antiviral drugs, particularly with new mechanism of antiviral action, high activity, and low toxicity is of great importance now.
There are known antiviral pharmaceutical compositions including as an active ingredient ethyl 6-bromo-4-[(dimethylamino)methyl]-5-hydroxy-1-methyl-2-(phenylthiomethyl)-1H-indole-3-carboxylate hydrochloride (Arbidol) [Arbidol, PCT Int. Appl. WO 9008135, 1990]

Arbidol is used for prophylaxis and treatment of diseases caused by viruses of influenza. It demonstrates the ability of inducing interferon and shows the immunomodulating effect. [Arbidol. Drugs R. D. 1999, September; 2(3), 171-172. Glushkova, T.; Glushkov, R. Arbidol—Interferon inductor, immunomodulator, antioxidant. Rev. Esp. Quimioter. 2000, 13(Suppl. 2), Abstr. M182]. Recently, antiviral activity of Arbidol against avian influenza viruses A/H5 was shown [Fedyakina I. T., Leneva I. A., Yamnikova S. S., Livov D. K., Glushkov R. G., Shuster A. M., Sensibility influenza viruses A/H5 recovered from wild birds on the territory of Russia to Arbidol in cell culture MDCK. Virology Problem, 2005, 50(6), 32-35], and Arbidol suppressing activity towards viruses of hepatitis C (HCV) was discovered as well [Y. S. Boriskin, E. I. Pécheur, S. J. Polyak. Arbidol: a broad-spectrum antiviral that inhibits acute and chronic HCV infection. Virology Journal 2006, 3:56 (http://www.virologyj.com/home)].
However, the main disadvantage of Arbidol is its high cellular toxicity (CC50=10-20 mM) and, as a result of it, small therapeutic window or low selectivity index (SI50). For example, for influenza virus it is equal only to 2.69 (on cellular line MDCK TC50=62.5 μg/ml and IC50=23.2 MκΓ/ml) [PCT Int Appl. WO 2005/087729 A1, 2005]. Its toxicity is even higher on some other cellular lines (TC50=15-25 μg/ml) [Brooks M J: Studies with the antiviral drug arbidol [PhD thesis]. Melbourne, Australia: RMIT University; 2003].
There are known antiviral pharmaceutical compositions comprising as an active ingredient Arbidol analogs of the general formula A. [PCT Int Appl. WO 2004060873, 2004; PCT Int Appl. WO 2005/087729 A1, 2005. Bioorg. Med. Chem. 2006, 14(4), 911-917].
wherein: R1 is alkyl or cycloalkyl; R14 and R24 independently of each other are amino group substituents selected from hydrogen, optionally substituted alkyl, optionally substituted cycloalkyl, optionally substituted aryl or optionally substituted heterocyclyl, or R14 and R24 together with the N-atom they are attached to via R14 and R24 give rise to optionally substituted azaheterocyclyl; W is a substituted mercapto group.
Arbidol analoges of the general formula A also exhibit suppressing activity towards viruses of influenza A and B, as well as to viruses of hepatitis B (HBV) and human immunodeficiency virus (HIV) [Bioorg. Med. Chem. 2006, 14(4), 911-917. PCT Int Appl. WO 2005/087729 A1, 2005]. However, Arbidol analoges of the general formula A, as well as Arbidol itself, show high cellular toxicity and, as a result of it, low selectivity index. Thus, for example, selectivity index for this series of compounds towards hepatitis B is, as a rule, <10 (SI50=1.81-10.8) [Bioorg. Med. Chem. 2006, 14(4), 911-917].
There are also known substituted indoles representing 1,2,3,7-tetrahydropyrrolo[3,2-f][1,3]benzoxazines exhibiting properties of selective M-4 muscarinic antagonists, potentially suitable for treatment of Parkinson disease [Augelli-Szafran, C. E.; Jaen, J. C.; Moreland, D. W.; Nelson, C. B.; Penvose-Yi, J. R.; Schwarz, R. D. Identification and characterization of m4 selective antagonists. Bioorg. Med. Chem. Lett. 1998, 8(15), 1991].
6-Methyl-1,2,3,7-tetrahydropyrrolo[3,2-f][1,3]benzoxazine-5-carboxylates B[DE 2408603, 1974; DE 2462471, 1977] also demonstrate various types of biological activity.

However, substituted 1,2,3,7-tetrahydropyrrolo[3,2-f][1,3]benzoxazines with antiviral activity have not been known yet.
Searching for highly effective antiviral drugs is now one of the main directions of the development of new pharmacological remedies for treatment of wide and diversified range of virus infections. For this reason working out of new compounds of this type, the pharmaceutical compositions including these compounds, and antiviral drug substances on their bases, methods for their preparation and application are of vital importance.